in a conventional electrophotographic image forming apparatus for forming a toner image on a photosensitive body, various controls have been proposed, in order to prevent degradation in image quality. For example, Japanese Patent Application Publication No. Hei-02-87176 discloses a configuration that handles variations in the charging characteristics of a photosensitive body with time. In this configuration, a varying degree, by which the charging characteristic of a photosensitive body varies with time, is determined in advance based on a relation between a charging voltage and a surface potential of the photosensitive body, and the charging voltage is adjusted dependently on the determined varying degree of the charging characteristics with time.